Tremolo



Jan 10, 1961 J. RICE 0 TREMOLO 7 Filed Jan. 11, 1954 DUAL FREQ.

CONTROL INVE TOR YWL WWW United States Patent TREMOLO Joseph Rice,103-26 68th Ave., Forest Hills, Queens, NY.

Filed Jan. 11, 1954, Ser. No. 403,394

1 Claim. (Cl. 179-1) This invention relates to a tremolo for use withmusical devices.

A tremolo effect is often desired for musical instruments and isgenerally somewhat difiicult to obtain. Some devices have been tried,and in many cases introduced distortions and extraneous signals whichwere of irritating proportions.

It is a prime object of the invention to provide an electronic tremolowhich may be utilized with instruments normally connected to electronicamplifier circuits.

It is a further object of the invention to provide an improved tremolohaving a variable frequency range.

It is another object of the invention to provide an improved tremolowhich is economical to manufacture and positive in action.

In general, the invention comprises an electron tube amplifier to theoutput whereof is inserted a low frequency wave for modulating a signalpassing through the amplifier.

The invention is more fully described in the following specificationtaken with the figure which is a circuit diagram of an illustrativeamplifier and low frequency generator embodying the invention.

Referring to the drawing in detail, an electron tube such as a triode isconnected in an electrical circuit to function as an audio amplifier.The triode, for example, may conventionally be a half section of a l2AX7electron tube or any other single or multi-purpose tube. The circuit asshown, includes an audio-input circuit which is connected to grid 12across a load resistor 14 which is connected to a grid 12 at oneextremity and the other extremity thereof is connected to a referencepoint as B-. A cathode 16 is connected to the reference point or B-through a bias resistor 18 shunted by a capacitor 20. Positive potentialfrom the B+ terminal of the power supply is connected to anode 22through a resistor 24. This generally completes the circuit of aconventional type audio amplifier, the output whereof is taken from theanode 22 through a capacitor 26 and applied across a load resistor 28. Alow frequency oscillator is formed as a phase shift oscillator andutilizes a second triode 30 which may be the second half of amulti-purpose electron tube such as the l2AX7 heretofore mentioned. Thecircuitry of the oscillator comprises a grid bias circuit for the phaseshift formed by a capacitor 32 and resistor 34 one extremity of eachbeing connected to a grid 36. The other extremity of resistor 34 isconnected to the cathode 38 of tube 30. Frequency control isaccomplished by means of a dual potentiometer 40 the center arm whereofand one extremity of each section are likewise connected to cathode 38.To provide a frequency range within desired limits a resistor 42 isconnected to one of the potentiometer elements and a resistor 44 isconnected to the other potentiometer elements. Capacitor 32 is connectedto one extremity of resistor 42 and through a capacitor 46 to oneextremityof resistor 44 and through a further capacitor 48 to the anode50 and triode 30. Anode pop CC tential is obtained from a 3+ terminal ofa source of supply through a resistor 52, to anode 50.

The phase shift oscillator is controlled by means of an on-ofi switch 54which is in series with a resistor 56 and the cathode 38, of tube 30.Output from the oscillator is taken off between cathode 38 and anode 50.The heart of the invention resides in the modulation of the outputsignal from the audio-amplifier by the output signal from the lowfrequency amplifier and is accomplished through a bridge networking 58formed of four diodes A, B, C, D and having a resistor 60 as a load. Theoperation of this bridge will be hereafter discussed.

To suitably match the load resistor 60 the oscillator output is coupledthrough capacitor 62 and 64 to an H pad E formed of resistors 66, 68,70, 72 and variable resistor 74. The output signal is taken off loadresistor 76 through a capacitor 78.

In operation the audio-amplifier amplifies a signal which appears acrossload resistor 28 and is coupled to load resistor 28 and load resistor76. On one half cycles output current flows through diode C bridgeresistor 60 and diode B and on the other half cycles flows through diodeA bridge resistor 60 and diode D. Simultaneously with this flow ofcurrent a modulating signal from the low frequency generator obtainedfrom the H pad E is applied across bridge load resistor 60 through wiresF and G. In this manner signals appearing across bridge load resistor 60are affected by the modulating signal obtained from the low frequencyoscillator. This modulation results in the tremolo effect.

The phase shift oscillator is balanced for its output facilitatinginjection to the balanced modulator or bridge network. Balance isaccomplished by means of substantially equal value load resistors in thecathode and anode circuit.

Although I have discussed my invention as it is utilized with one typeof audio-amplifier and one type of low frequency oscillator, it isobvious that other types of audioamplifiers, oscillators and other tubesmay be utilized with equal results.

In the invention typical values of components utilized with the circuitembodying the invention is herein disclosed as follows:

Resistor 14 ..ohms 470K H Resistor 18 do 1K Resistor 24 -do K Resistor28 do 47K Resistor 34 megohms 2.7 Resistor 42 ohms 100K Resistor 44 do100K Resistor 52 do 100K Resistor 56 do 100K Resistor 60 do.. 47KResistor 66 do K Resfstor 68 do 150K Resistor 70 do 150K Resistor 72 do150K Resistor 76 do 47K Capacitors 20 tnfd 50 Capacitors 26 'mfd .1Capacitors 32 mfd .01 Capacitors 46 ..mfd .01 Capacitors 48 n mfd .01Capacitors 62 mfd .5 Capacitors 64 -mfd .5 Capacitors 78 mfd .1 Dualpotentiometer 40 megohms l Potentiometer 74 do 5 Having thus describedmy invention I desire it understood that variations thereof will beobvious to those a '4 skilled in the art and the claim appended heretobe interand means for impressing the predetermined low frepreted withinthe spirit and scope of the'invention; quency signal fromsaid lowfrequency 'o'scillator across What is claimed is: said low resistor. Atremolo including an audio frequency amplifier, a

19w firequency oscillator means for adjusting said 5 References Cited inthe file of this patent frequency oscillator to a predetermined constantfrequen UNITED STATES PATENTS cy and means for mixing a signal passingthrough said 2,233,860 Wise Man 4, 1941 audio amplifier with thepredetermined low frequency 2 4 5 533 Rowe Oct 1 1949 signal from saidlow frequency-oscillator, said means in- 2,534,342 Da i l D 19, 1950eluding a bridge rectifier circuit including a low resistor 10 2,682,640Harling June 29, -1954

